Background Cardiac-specific overexpression of TNF-α in vivo produces a dilated cardiomyopathy. Studies in our lab have demonstrated that cardiac myocyte apoptosis is increased in TNF-α overexpressing transgenic (Tg) mice; however, TNF-α treatment alone does not increase apoptotic rates in cultured cardiac myocytes. We explored the effects of TNF-α on cultured cardiac myocytes expressing an apoptotic “sensitizer” (c-Myc) elevated in failing myocardium. The role of apoptosis in heart failure (HF) progression in TNF-α Tg mice was determined by treatment by D-4F, an apolipoprotein A-1 mimetic peptide that has been shown to favorably alter the inflammatory properties of HDL.
Methods Neonatal rat ventricular myocytes (NRVMs) were infected with an adenovirus overexpressing human c-Myc (AdMyc) or a virus expressing LacZ as a negative control (AdLacZ). Virus-infected cells were treated with 20 ng/μL TNF-α for 12 h and assessed for apoptosis by TUNEL staining. In vivo studies used wild-type (NTg) or Tg mice expressing human TNF-α in adult myocardium treated with D-4F or saline beginning at week 4 of life, and sacrificed at week 8. Hypertrophy was assessed by heart mass. Cardiac function was assessed by 2-D echo. Myocyte morphology was studied by H&E sectioning and apoptosis was quantified by TUNEL staining.
Results c-Myc overexpressing NRVMs treated with TNF-α showed a 2-fold increase in apoptosis compared to untreated c-Myc overexpressing myocytes (p < .05). There was no significant difference in apoptosis between AdMyc infected cells not treated with TNF-α or TNF-α-treated AdLacZ infected cells and non-infected controls. In vivo, TNF-α Tg mice, when compared to NTg mice, demonstrated adverse LV remodeling (EDD 4.6 ± 0.2 mm vs 3.82 ± 0.26 mm, p < .05), reduced cardiac function (LVEF% 49.5 ± 15 vs 63.2 ± 9.3, p < .05), and increased cardiac hypertrophy measured by heart weight to body weight ratio (7.1 ± 0.02 vs 5.2 ± 0.47 mg/g, p < .01). Treatment with D4-F completely inhibited the adverse remodeling in TNF-α Tg mice and reduced apoptotic rates.
Conclusions TNF-α induces cardiac myocyte apoptosis in vitro when sensitized by c-Myc. TNF-α-induced LV remodeling and heart failure in mice is attenuated by treatment with D-4F, possibly through a reduction in cardiac myocyte apoptosis. These models will provide useful tools to explore the mechanisms of TNF-α action and beneficial effects of D-4F.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.